[Devel] [PATCH RHEL7 COMMIT] mm: Fix mis accounting of isolated pages in memcg_numa_isolate_pages()

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-693.1.1.vz7.37.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-693.1.1.vz7.37.27
------>
commit 01b3a23d466d41c3d54e8700e58785e2357e053b
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Mon Nov 13 15:24:40 2017 +0300

    mm: Fix mis accounting of isolated pages in memcg_numa_isolate_pages()
    
    When split_huge_page_to_list() fails, and a huge page is going back
    to LRU, the number of isolated pages is decreasing. So we must
    subtract HPAGE_PMD_NR from NR_ISOLATED_ANON counter, not to add it.
    
    Otherwise, we may bumped into a situation, when number of isolated
    pages grows up to number of inactive pages, and direct reclaim hangs in:
    
      shrink_inactive_list()
         while (too_many_isolated())
            congestion_wait(BLK_RW_ASYNC, HZ/10),
    
    waiting for the counter becomes less. But it has no a chance
    to finish, and hangs forever. Fix that.
    
    https://jira.sw.ru/browse/PSBM-76970
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 mm/memcontrol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a7fa84a..a165a22 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4963,7 +4963,7 @@ static long memcg_numa_isolate_pages(struct lruvec *lruvec, enum lru_list lru,
 		if (PageTransHuge(page) && split_huge_page_to_list(page, dst)) {
 			list_del(&page->lru);
 			mod_zone_page_state(zone, NR_ISOLATED_ANON,
-					HPAGE_PMD_NR);
+					-HPAGE_PMD_NR);
 			putback_lru_page(page);
 		}
 	}